The development of optical radiation detectors in conjunction with the Naval Research Laboratories has resulted in a detection system that employes the accelerator gun trigger pulses as an electronic gate for data acquisition; thereby eliminating the field and dose rate dependent contaminant due to Cerenkov radiation. The resulting detector is small and very sensitive, with a linear response and a wide dynamic range. Phantom studies have been performed and limited clinical deployment is underway. The initial phase is to stude the clinical utility of a small number of discrete fibers in dose verification. The next step is to develop an array of fibers as either a rectangular or spiral grid and study the dose map generated during radiotherapy and the effect of small changes in organ or beam positioning. The third phase is to understand the meaning of signal change relative to the patient's anatomical position and to interrupt the treatment if detected signals differ from reference values by a predetermined tolerance margin. The fourth and final phase is to dynamically link the changes in grid signals to corrective changes in the radiation field for on-line, dynamic dose control of radiation treatments.